This project is designed to examine the interrelation of the immune system and neoplasia of the central nervous system spontaneously arising in patients and virally induced in experimental animals. Sequential immunologic data including analysis of the various lymphocyte subpopulations are collected from these subjects and are correlated with the clinical course, treatment, and tumor size. Mechanisms for the observed host impairment of cell-mediated immunity via humoral and cellular suppressor factors will be examined in both models.